The present invention relates to an electric motor bicycle, and more particularly to a unitary self-contained direct drive power module (or xe2x80x9cunitary power modulexe2x80x9d) for electric bicycles or other vehicles. The invention also includes a kit for converting a standard bicycle into an electric bicycle by use of the unitary power module.
By way of background information, and turning now to the drawings, FIG. 19(a) illustrates a standard bicycle 100 (xe2x80x9cor bicyclexe2x80x9d), which is a two wheeled vehicle comprised typically of a front steering wheel 102 and a rear wheel 104, which may be attached to the frame by quick-disconnect units 105. The standard bicycle 100 includes a frame assembly 106 having a head tube 108 which journals a front fork 110 for steering via handle bars 109 by a rider of the bicycle 100. As illustrated in FIG. 19(b), the rear wheel 104 is journalled at the rear end of the frame 106 by a pair of rear stays (or xe2x80x9cdropoutsxe2x80x9d) 112. A seat tube 111 is carried by the frame 106 adjacent the rear wheel 104 and a seat post 113 upon which a saddle type seat 115 is positioned thereon to accommodate a rider.
In the standard bicycle 100, a horizontally oriented journal (or crank journal) 117 is positioned beneath the seat tube 111 which supports a rider xe2x80x9cpropelledxe2x80x9d drive mechanism 120. The drive mechanism 120 generally comprises a crank 123 journalled in the crank journal 117, which includes a chain sprocket 129 having a plurality of teeth, together with the crank 123 positioned therein with along with pedals 125 rotatably journalled at each end 127 of the crank 123.
Each wheel typically consists of a tire 114 mounted on a rigid rim 116, an axle 118, a hub mechanism (or xe2x80x9chubxe2x80x9d) 122 and spokes 124 connecting the rigid rim 116 to the hub 122 to form an axle/hub assembly 121. The hub 122 surrounds the axle 118 and is free to rotate about the axle 118 through a bearing assembly 126 (not shown). The tire/rim assembly 128 is attached to the hub 122 through an assembly of the spokes 124 which are assembled in a woven pattern 130 to form a wheel/hub assembly 140. This woven pattern 130 of spokes has relatively few variations with a large quantity of existing bicycle wheels being common in using the same or similar thirty-six or thirty-four spoke weave pattern 130. A target xe2x80x9cchainxe2x80x9d sprocket 150 is mounted about the rear wheel 104, and is connected to the crank sprocket 129 by a chain 152 whereby application of power by the rider on the pedals 125 propels the bicycle 100. A derailleur 154 is often substituted for the single target sprocket 150 (or target sprocket), and may have a plurality of sprockets 156, 158, 160, 162, 164 and 166 (illustrated in FIG. 9) to provide variable gearing for rider comfort when either starting or climbing hills or for rider efficiency.
One of the features of a bicycle, is the ability of the wheel to be removed for servicing, such as repairing a flat. As described above, the typical bicycle wheel is constructed of a tire/rim assembly connected to the hub through a series of woven spokes. The hub rides on the axle of the wheel using a bearing assembly. The axle/hub assembly typically has rather loose manufacturing tolerances and as such provides a poor reference frame for the propulsion elements of prior systems. This occurs because bicycles are typically high rate, low-cost, manufactured consumer products, whereby the tolerances of components are not as high as a high quality mechanism. The majority of bicycles sold in the world and in use are in the lower or looser tolerance ranges. Also, when the wheel (or tire) is repaired and then replaced in the dropouts of the frame, the axle can become slightly cocked with respect to the frame. As such, tolerances for the mounting slots of the wheel axle allow for a wide latitude of assembly. The loose manufacturing tolerances of the axle and axle/hub bearings is typical of such low-cost mechanisms. These large tolerances of wheel and bicycle frame components present a significant problem in the design of reliable direct drive propulsion systems where various components of the system are mounted on different parts of the bicycle (e.g., on the frame, on the axle, etc.)
If the various components of the propulsion system are mounted on bicycle components, which have loose tolerances in reference to each other, then the propulsion system suffers (or will suffer) from these same poor alignment tolerances with rough usage. In order to avoid excessive wear, reduced efficiency, and reduced performance as a result of such loose tolerances, an effective propulsion system should ideally utilize a design which is independent of such loose tolerances in the axle/hub assembly of the bicycle as well as the changing tolerances relative to the frame. It is this design concept which forms this invention.
In the past, electric propulsion systems for bicycles have been implemented through a variety of methods which utilized electric motor power to either supplement or replace the above rider drive mechanism in propelling the bicycle. For example, these methods include friction roller drives, belt drives, gear drives, and chain drives. For example, friction drives typically involve the application of an electric motor or xe2x80x9cthe drive sourcexe2x80x9d to a wheel or xe2x80x9cthe target mechanismxe2x80x9d through a roller mechanism. The roller may be directly attached to the drive source or through a clutch mechanism. The roller transfers the drive source energy through the contact of the roller on the target wheel through friction between their respective surfaces. This type of drive system suffers from mechanical losses associated with slippage between the roller mechanism and the target wheel as a result of reduced friction and from the energy required to compress the rubber tire. Performance in moisture, rain, snow and mud is marginal at best.
By way of further example, electric bicycles having direct drive systems, such as belt, gear and chain drives typically provide higher energy coupling efficiencies than the roller friction drive systems. These systems however require a high degree of mechanical integrity in the geometry of drive components. For instance, there needs to be sufficient tension in the belt and chain of the belt and chain drive systems and the proper alignment or meshing of the gears in the gear drive system. Proper and exact mechanical alignment must be maintained rigidly with shock and many tire and wheel repairs in order to extend the life of the unit.
There have been a number of designs, which can provide direct coupling between an electric motor(s) mounted externally to the rear bicycle wheel and the axle of the wheel. For example, a motor can be mounted either on the diagonal or horizontal rear members (or xe2x80x9cstaysxe2x80x9d) of the frame. A direct coupling in these cases can be effected through a 90-degree bevel gear between a shaft from the motor and the axle-hub assembly. In this case, external shocks will cause gear wear. Further, it is difficult to remove the rear wheel for repair. The drive can be effected through a chain, which is better but still mechanically complex and subject to the same kind of problems. It is also difficult to achieve the right reduction ratios between the RPM of typical motors and that of the rear wheel, typically between 10:1 and 25:1. A motor can be mounted above the rear wheel and drive a very large xe2x80x9csprocketxe2x80x9d of diameter almost as large as the wheel diameter. Such systems have been demonstrated but have not been accepted because they are clumsy, top-heavy and subject to relative dislocation of the elements.
Other direct drives have been reduced to practice with the motor mounted in the neighborhood of the pedal crank. These can be coupled to the rear wheel by a gear drive with suitable clutches within the crank housing and thence through the usual bicycle chain or through a separate long chain to a separate sprocket on the rear wheel. They can also be coupled to the rear wheel through long shafts and bevel gears. While some of these are workable and practical, they require a special custom bicycle design, which may be more expensive than desired.
For designs in which a motor mounted externally to the rear wheel, an improvement is described in U.S. Pat. No. 5,934,401 entitled xe2x80x9cPrecision Direct Drive Mechanism for a Power Assist Apparatus for a Bicycle,xe2x80x9d by Mayer et al. filed on Feb. 20, 1997. In this concept, as depicted in FIGS. 20-23, a motor is mounted on a plate, which is separately indexed to the axle of the rear wheel. The motor drives a pinion gear (or pinion sprocket) which drives through meshed gears, a chain or a belt a target gear (or sprocket) that is separately indexed to the axle of the rear wheel, and is attached to the axle through a bearing or free-wheel clutch arrangement. That is, the motor-pinion assembly with its mounting frame and the target gear (or sprocket) are separately indexed off the axle, with the target gear (sprocket) actually indexed from the hub.
Thus, these elements in a benign environment are accurately aligned with respect one another, all being indexed from presumably common and concentric points. However, even with this improved and more compact configuration, we have found in practice that for most bicycles, the axle bearing tolerances and the hub bearing tolerances are highly variable with real world rough usage and shocks. In more detail, if the mesh between the pinion sprocket (or gear) and the target sprocket (or gear) occurs at a long leverage arm from the axle, the looseness of the bearings can change the pinion/target gear meshing or alignment, leading to eventual gear wear, tooth breakage, or misalignments of such sprockets. Additional concerns are the difficulty of achieving the alignment of shafts (such as the shafts of the motor, or the target wheel) and the manufactured tolerances of components over time and with normal rough usage.
Another class of direct drive systems are based on xe2x80x9chub motorsxe2x80x9d which are designed into the wheel hubs of front or rear wheels. This class of drives has its own cost considerations and performance characteristics.
None of the above described electric bicycle drive propulsion systems provides the important advantages of the inventive unitary power module for an electric bicycle propulsion system which has a high degree of mechanical integrity in the alignment geometry of the drive components even under shock and rough usage. These advantages are achieved by uniquely configuring the unitary power module having drive components comprising a drive source (or an electric motor), a pinion drive coupling component (such as a chain sprocket, gear or pulley pinion or combination thereof), a target mechanism coupling component (or a chain sprocket, driven gear, or belt sprocket), the actual mechanical coupling mechanism to the target or target wheel, and the target or driven wheel, itself, which is the normally the rear wheel. By use of various sprocket ratios, the invention may achieve a wide-range of gear ratios and therefore adaptability to a wide range of motors. Also, by the use of a free-wheel clutch incorporated into the unitary power module, the bicycle is completely free wheeling with virtually no drag in the absence of applied power. Still further, when in production, the unitary power module can be assembled and tested as an integral operating unit, and then be easily and simply attached to the bicycle frame.
Specifically, the present invention achieves these advantages by utilizing a unitary power module having mounting frame assembly on which all propulsion elements are mounted and aligned with a wheel fitting (or xe2x80x9cdrivexe2x80x9d) coupler, which is a disk shaped assembly with a large center opening allowing the target coupler to be placed about a wheel axle outside of the hub diameter. In the preferred embodiment, the target coupler has a groove pattern mating the woven spoke pattern of a bicycle wheel to enable the target coupler to be concentrically attached to the target wheel by engagement with the woven spoke pattern by securing elements. The mounting frame is attached to the target coupler by a bearing or the like, including a free wheel clutch. The mounting plate has an opening (or xe2x80x9celementxe2x80x9d) to receive an electric motor to enable a pinion sprocket or gear affixed on the motor to engage the sprocket and through a chain to the target sprocket (or gear) to rotate the target bicycle wheel upon suitable power application by a rider via propulsion controls on the bicycle.
Thus, the present invention provides the advantages of having a separate independent self-contained (and self-aligned) unitary power module which overcomes misalignment problems between the drive source and the target by using a common reference frame. The integrity of the chain alignment or gear mesh is thereby permanently ensured even in rough terrain and rough shock and usage. This invention can thus be advantageously implemented by using a chain drive, gear drive or belt drive system because one of its important advantages is its inherent avoidance of the usual misalignment causes by the above prior art devices. It has the additional advantage of being easily installed on almost any bicycle rear wheel by an unique and separately described mechanical coupler. It works efficiently, essentially independent of frame and axle/hub assembly and wheel/hub tolerances.
According to the invention, a unitary power module for mounting a propulsion system on a bicycle comprises a mounting frame having a motor and a target sprocket integrally mounted on the mounting frame. The target sprocket defines a disk shaped member having a center opening to allow the drive sprocket to be placed about a wheel axle of the bicycle. The drive sprocket mates with a bicycle wheel through a clutch and target coupler to enable the sprocket to be mounted substantially concentrically to an axle of the wheel by engagement with a wheel pattern of the bicycle by securing elements. The mounting frame is rotatably attached to the target sprocket to allow for xe2x80x9calignedxe2x80x9d rotation of the target sprocket about the wheel axle, and proper alignment with an electric motor. The mounting frame has an element to receive an electric motor to enable a pinion sprocket affixed to the motor to propel the target sprocket and rotate the bicycle wheel. In the manner, the mounting frame provides a single point of reference for aligning the pinion sprocket with the target sprocket, i.e., thereby allowing the unitary power module to operate by itself, for example on a bench, independent of the bicycle per se.
In another embodiment of the invention, a propulsion system kit is provided for converting a standard bicycle having a frame and front and rear wheel, with the rear wheel having an axle and hub together with a wheel pattern into an electric bicycle. The kit comprises a battery suitable to be affixed to the bicycle, an electric motor having a pinion sprocket (or gear) affixed thereon, with the electric motor suitable to be connected to the battery by a battery cable. A unitary member comprises a target sprocket, a mounting frame and gear reduction or chain mechanisms which are precisely aligned with each other. The target coupler sprocket comprises a disk shaped assembly having an center opening to allow the unitary member to be placed around the axle outside the hub. The target coupler has a pattern which mates a pattern of the rear wheel to the target sprocket to enable the target sprocket to be concentrically attached to the wheel spokes by engagement with the spoke pattern by securing elements. The mounting frame is rotatably attached to the unitary member by a bearing or the like and has an opening to receive the electric motor to enable the driver to engage the target sprocket for aligned rotation of the wheel upon application by the rider of electrical propulsion controls affixed to the bicycle. The free wheel clutch can be mounted either in the motor-pinion sprocket shaft or in the wheel attachment mechanism. Thus, the mounting frame provides a single point of reference for aligning the pinion sprocket with the target sprocket.
In yet another embodiment of the invention, an electric bicycle comprises a frame having a rider seat and propulsion controls positioned thereon. A steerable front wheel has an axle affixed to a front portion of said frame, together with a rear wheel having an axle with a wheel pattern affixed to a rear portion of the frame. A propulsion system comprises a battery affixed to the bicycle, and an electric motor having a driver affixed thereon the electric motor suitable to be connected to the battery by a battery cable. A unitary power module comprises a target coupler and a mounting frame, with a target coupler comprising a disk shaped member having an center opening to allow the drive member to be placed about the wheel axle. The target coupler is affixed to the rear wheel to enable the target sprocket to be concentrically attached to the rear wheel by engagement with the wheel by securing elements. The mounting frame is secured to a fixed portion of the frame in order to transmit torque and is attached to the unitary member through a bearing or the like and has an opening to receive the electric motor to enable the driver to engage the target sprocket for aligned rotation of the rear wheel upon application by the rider of the propulsion controls. Thus, the mounting frame provides a single point of reference for aligning the pinion sprocket with the target sprocket.
Preferably, in accordance with the invention, a unitary power module for mounting a propulsion system on a bicycle comprises a target sprocket defining a disk shaped member having a center opening to allow the target coupler to be placed about a wheel axle of the bicycle. The target coupler mates a bicycle wheel to enable the sprocket to be substantially concentrically attached to said wheel by engagement with said woven spoke pattern by securing elements. A mounting frame is rotatably attached to the target sprocket to allow for rotation of the target sprocket about the wheel axle and has an opening suitable to receive an electric motor to enable a driver sprocket affixed to the motor to engage a second sprocket mounted by a second shaft positioned on the mounting frame. The second sprocket shaft is positioned to drive the target coupler and rotate the bicycle wheel.
In another preferred embodiment, a propulsion system kit is provided for converting a standard bicycle having a frame and front and rear wheels, with each having a hub, axle and a wheel spoke pattern, into an electric powered bicycle. A battery suitable to power an electric motor is affixed to the bicycle, together with an electric motor having a driver affixed thereon. The electric motor is suitable to be connected to the battery via a battery cable. An unitary power module for mounting a propulsion system on a bicycle comprises a target sprocket defining a disk shaped member having a center opening to allow the target sprocket to be placed about a wheel axle of the bicycle with the target sprocket mating the bicycle wheel pattern to enable the sprocket to be substantially concentrically attached to the wheel by engagement with the pattern by securing elements. A mounting frame is aligned to and rotatably attached to the target sprocket to allow for aligned rotation of the target sprocket about the wheel axle and has an opening to receive the electric motor, which enables the driver to engage a second sprocket positioned thereon. The second sprocket is mounted on a second shaft which engages the target sprocket to propel the target sprocket and rotate said bicycle wheel upon application by a rider of propulsion controls positioned on a bicycle frame. The mounting frame provides a single point of reference for aligning the pinion sprocket with the target sprocket.
In yet another preferred embodiment, an electric bicycle comprises a frame having a rider seat and propulsion controls positioned and thereon. The bicycle includes a steerable front wheel having an axle affixed to a front portion of the frame, and a rear wheel having an axle with a pattern affixed to a rear portion of the frame. A propulsion system for the bicycle comprises a battery affixed to the bicycle, and an electric motor having a driver affixed thereon, the electric motor suitable to be connected to the battery by a battery cable. A unitary power module for mounting a propulsion system on the bicycle comprises a target sprocket defining a disk shaped member having a center opening to allow the target sprocket to be placed about a wheel axle of the bicycle. The target sprocket mates with a bicycle through a wheel coupler to enable the target coupler to be substantially concentrically attached to the wheel by engagement with the wheel pattern by securing elements. A mounting frame is aligned and rotatably attached to the target sprocket to allow for aligned rotation of the target sprocket with the driver about the wheel axle and has an opening to receive the electric motor to enable the driver affixed on the motor to engage a second sprocket positioned on a shaft. The second sprocket shaft is disposed to engage the target sprocket to propel the target sprocket and rotate the bicycle wheel upon application by a rider of propulsion controls positioned on the bicycle. The mounting frame provides a single point of reference for aligning the pinion sprocket with the target sprocket.
Preferably, the above embodiments having the second sprocket and shaft include a third sprocket concentrically mounted upon with the second shaft, with the driver rotating the second sprocket, which in turn rotates the third sprocket which is positioned to engage the target sprocket.
In more detail, and by way of example, the target sprocket is preferably attached to the mounting frame by a bearing. Further, a one way clutch is affixed between the pinion sprocket and the motor.
Still further, the target coupler (or target sprocket) may include a groove pattern disposed to mate a woven spoke pattern of the bicycle wheel, or simply mate with a hub positioned on the bicycle wheel.
Further, the pinion sprocket may engage the target sprocket (or second sprocket and third sprocket as appropriate, by either the target sprocket and driver each having a plurality of teeth suitable to be connected in power engagement a drive chain; or each having a plurality of gear teeth suitable to be engaged by one another, or each having a surface suitable to be engaged by a drive belt.
Furthermore, the electric motor may quickly be engaged or released from the mounting frame by a series of quick release tabs, together with connecting or disconnecting the motor shaft with a unitary power module shaft by using gears or spline connections.
According to the invention, a disk shaped member for an electric bicycle propulsion system preferably comprises a target sprocket comprising a disk shaped assembly having an center opening to allow target sprocket member to be placed about a wheel axle, and woven spoke pattern which allows the target sprocket to mate the woven spoke pattern of a wheel to enable the sprocket to be concentrically attached to the wheel outside the hub diameter by engagement by securing elements.
Further, a mounting frame for an electric bicycle propulsion system has a first and second opening disposed to receive an electric motor, and target sprocket, respectively. The target sprocket is securable to a bicycle wheel and securable to the mounting frame about a bearing affixed about the second opening.
As pointed out in greater detail below, the embodiments of this invention provides a number of significant advantages. For example, the key points of the invention include the establishment of a common reference or mounting frame and structure which assures precision alignment for the entire propulsion system under all conditions. This reference frame is formed by the disk or target sprocket along with the hollow extension collar and grooved surface. This disk provides a solid mounting attachment with the wheel through the grooved surface mating with the wheel hub and spokes. The disk is held concentric with the wheel hub, but great eccentricity accuracy is not required. The sprocket gear is attached to the reference frame disk through either a freewheeling clutch or directly attached to the reference frame disk. The motor mounting frame is attached to the reference frame disk through a bearing on the hollow extension collar of the disk. The motor is attached to the motor mounting frame, in such a way as to provide for proper meshing of the driven and target sprocket, independent of axle and hub bearing tolerances. The driver sprocket (or gear) is attached to the motor either directly, or through a one-way roller clutch, depending on whether the driven (or sprocket) gear has a freewheeling clutch. In this manner, the pinion sprocket, target sprocket and any intermediate gears are precisely aligned irrespective whether they are interconnected by a chain, a gear, or a belt. The motor mounting frame is clamped to the bicycle frame to prevent rotation of the mounting frame, i.e., to transmit propulsion torque to the bicycle.
The invention holds the entire propulsion system within the same reference frame, thereby constraining the propulsion system tolerances within the propulsion system. These tolerances are determined by the manufacturing tolerances of the propulsion system components as designed independent of the vehicle manufacturing tolerances. This allows the propulsion system to be applied to any vehicle, while maintaining the integrity and performance of the propulsion system. The invention itself, together with further objects and attendant advantages, will best be understood by reference to the following detailed description taken in conjunction with the accompanying drawings.